1. Field of the Invention
This invention relates to valves and, more particularly, to ball relief valves.
2. Prior Art
Ball valves having a valve body with an internal valve seat closable by a spring urged ball are well-known to the art and have been extensively used for many years. Such devices usually have a passageway through the body with a reduced diameter valve seat formed interiorly of the body either by a ledge formed in the passageway or by the insertion of a separate valve seat member. The ball is placed downstream of the valve seat and is spring urged toward the valve seat. In such constructions, sealing occurs between the periphery of the valve seat and the outer surface of the ball. When pressure builds on the upstream side of the seat to an extent where the total pressure against the exposed surface of the ball interior of the seat inner periphery exceeds the pressure of the spring against the ball, the ball will unseat and pressure will be relieved past the ball.
Such known devices have a singular disadvantage in that in order to provide a good seal both the valve seat and the ball surface must be highly polished by machining or coining or the valve can leak. Even when properly manufactured such valves are not considered to be air tight.
In order to reduce this, it has been known to use frustoconical valve seats and non-ball valves. Such non-ball valves have included devices having frustoconical exterior surfaces having tapers substantially the same as the taper of the frustoconical valve seat, tapered stoppers having tapers different than the taper of the valve seat and, in some instances, stoppers having additional sealing members such as O-rings. Such an O-ring seal is shown, for example, in U.S. Pat. No. 2,481.482, which also illustrates a tapered stopper and valve seat. Such devices however, have a further disadvantage in that they have two seal surfaces, i.e. at the juncture of the O-ring seal with the valve seat and at the wall of the O-ring groove.
Although these devices have worked as both pop relief valves, for the most part, they still rely upon the use of metallic sealing members.
Elastomeric sealing members, such as O-rings and synthetic or natural rubber balls, have a known disadvantage in that they will cold flow under the influence of pressure. Over prolonged periods of time this can result in the elastomeric sealing member either being extruded through the valve seat opening or being distorted into the valve seat to a point where it will no longer seal properly and will not open at the desired pressure differential. It would therefore be an advance in the art to provide a pressure release valve or pop valve which utilizes an elastomeric seal member to reduce the expense necessary in production of polished mating seal faces but which, however, is provided with means preventing distortion or cold flow of the elastomeric member from occuring, and preventing extrusion of the elastic member through the valve seat.